Non-provisional patent application Ser. No. 10/820,930, filed on Apr. 8, 2004, described an invention which can replace incandescent light bulbs with more efficient light emitters such as light-emitting diodes (LEDs). The Background section of that patent application provided the justification for doing so, and it is incorporated herein by reference.
However, the description of the embodiment of that invention of that prior patent application and its claims prescribed circuitry which fit within the 3-d spatial envelope defined by the incandescent bulb, which is replaced by an instance of that prior invention. Furthermore, although instances of that invention would include flashlight bulbs, it did not focus in particular on the problem imposed by flashlights with tiny incandescent bulbs. The above-referenced, previous patent application described circuitry using current off-the-shelf components and a printed circuit board to employ them. Although it may be technologically possible, it is not economically attractive to implement that invention in a form that will fit entirely inside the spatial envelope of certain tiny standard incandescent light bulbs. For example, a so-called “grain-of-wheat” bulb is aptly named and would present an implementation challenge to fit all the circuitry of the above invention, as well as a light-emitting, solid state, semiconductor chip in such a small volume at a reasonable cost for a consumer product. This would currently apply to any light bulb which is, for instance, less than about 5 millimeters in diameter.
Therefore, in light of the foregoing limitation, the first objective of this invention is to provide a replacement light source for very small incandescent bulbs which employs the principles and circuitry of the aforementioned prior patent application, but where the invention is not limited in size by the envelope of the bulb it is replacing. Implicit in this first objective is the more efficient use of the batteries than with an incandescent bulb: providing longer battery life for the same light intensity or providing brighter light for the same battery life or a compromise in-between. Also implicit in the first objective is presumed advantage that solid state light emitters have over incandescent filaments regarding their relative expected operational lifetimes.
A second objective is to do this is a way which minimizes the cost and the effort for a consumer to retrofit the replacement. A third objective is to provide a replacement light source which fits entirely within the envelope of a commercially available, consumer flashlight, and which ideally still uses the type and same number of batteries for which the flashlight was designed. A fourth objective is to preserve the attractive features possessed by the flashlight before the incandescent bulb was replaced. These features may include, for example, user-adjusted beam focus and the on-off switch function (which itself may be integrated with the beam focus feature).
The principal advantage of such an illumination device is that the advantages of solid state illumination can be more quickly offered to consumers for a variety of existing flashlight models, without requiring them to buy a new, custom-designed flashlight. It also allows the consumer to revert back to the incandescent bulb if necessary.